In my previous post
http://legalsmeagol.blogspot.com/2010/02/star-trekthe-next-generation-and-deep.html
I described the following 'non-commissioned' chains of
command for the different Starfleet branches:

Command
1.Lieutenant (junior grade)
2.Ensign
3.Yr 4 cadet
4.Yr 3 cadet
5.Yr 2 cadet
6.Yr 1 cadet

Engineering and Security
1.Lieutenant
2.Chief Petty Officer
3.Lieutenant (junior grade)
4.Petty Officer
5.Ensign
6.Engineering or Security Rating


Science and Medical
1.Lieutenant-Commander
2.Lieutenant
3.Lieutenant (junior grade)
4.Ensign
5.Enlisted First Class
6.Enlisted Second Class

however, the geek that I am has realised that there are
no appearances of Lieutenant (junior grade)
for the Engineering/Security branch, and that the writers of
'Deep Space Nine' added the ranks of 'Senior' and 'Master'
CPO making the previous estimation of comparative ranks
questionable.


[Updated Engineering/Sec c-of-c:
1.Lieutenant (=Master Chief Petty Officer?)
2.Senior Chief Petty Officer
3.Chief Petty Officer
4.Ensign
5.Petty Officer
6.Engineering or Security Rating]

Of course,ST is rarely entirely consistent
but these points do need to be made.

Certainly, Command and Science/Medical can be compared
as follows:

1.Lieutenant (junior grade)
2.Lieutenant-Commander [Sci/M]
3.Lieutenant [Sci/M]
4.Lieutenant (junior grade)[Sci/M]
5.Ensign
6.Yr 4 cadet
7.Yr 3 cadet
8.Yr 2 cadet
9.Yr 1 cadet
10.Enlisted First Class
11.Enlisted Second Class

and the Engineering and Security ranks can thus be added
in a more simplified fashion in comparison with the other
ranks as follows (if certain ranks are considered otherwise
equal):

1.Lieutenant (junior grade) [C]
=Lieutenant-Commander [Sci/M]
=Master Chief Petty Officer
{roughly equivalent to:Regimental Sergeant-Major}

2.Lieutenant [Sci/M]
{Sergeant-Major}

3.Lieutenant (junior grade)[Sci/M]
{Warrant Officer (Class One)}

4.Senior Chief Petty Officer
{Warrant Officer (C2)}

4.Ensign [C]=Chief Petty Officer
{Staff Sergeant}

5.Ensign [E/S]=Ensign [Sci/M]
{Sergeant}

6.Yr 4 cadet
=Petty Officer
{Acting Sergeant}

7.Yr 3 cadet
=Engineering/Security Rating
{Corporal}

8.Yr 2 cadet
=Enlisted First Class
{Lance Corporal}

9.1st Year cadet
=Enlisted Second Class
{Private}

This is also more consistent with the command structure
in 'Deep Space Nine'